I know it is politically incorrect to ask this, but is there any reason to doubt that 'breeds' of humans exist, endowed with distinct traits and characteristics, just as there are certainly distinct breeds of dogs and horses? No one would doubt a greyhound and a thoroughbred are great runners, versus a dachshund or a plowhorse, for example. Same species, able to reproduce with other breeds. The analogy seems clear to me for humans. What am I missing?